Re: [PATCH 2/2] selftests/mm: verify droppable mappings cannot be locked

[anthony . yznaga]

On 4/2/26 12:28 AM, David Hildenbrand (Arm) wrote:
> > +
> > +/*
> > + * Droppable memory should not be lockable.
> > + */
> > +static void test_mlock_droppable(void)
> > +{
> > +	char *map;
> > +	unsigned long page_size = getpagesize();
> > +
> > +	/*
> > +	 * Ensure MCL_FUTURE is not set.
> > +	 */
> > +	if (mlockall(MCL_CURRENT))
> > +		ksft_exit_fail_msg("mlockall(MCL_CURRENT): %s\n", strerror(errno));
> Why do we need the prior mlockall()? If that is really required, the
> comment should be clearer why the munlockall() is insufficient.

The mlockall() is not needed. Will remove.


> Also, why can't we fail only the test?

The tests can be failed without the exit. I'll update them.

Thanks,
Anthony

> > +	if (munlockall())
> > +		ksft_exit_fail_msg("munlockall() %s\n", strerror(errno));
> Why can't we fail only the test?
>
> > +
> > +	map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
> > +		   MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
> > +	if (map == MAP_FAILED) {
> > +		if (errno == EOPNOTSUPP) {
> > +			ksft_test_result_skip("%s: MAP_DROPPABLE not supported\n", __func__);
> > +			return;
> > +		}
> > +		ksft_exit_fail_msg("mmap error: %s\n", strerror(errno));
> same.
>
> > +	}
> > +
> > +	if (mlock2_(map, 2 * page_size, 0)) {
> > +		munmap(map, 2 * page_size);
> Not required when exiting either way?
>
> > +		ksft_exit_fail_msg("mlock2(0): %s\n", strerror(errno));
> > +	}
> > +
> > +	ksft_test_result(!unlock_lock_check(map, false), "%s: droppable memory not locked\n",
> > +			__func__);
> > +
> > +	munmap(map, 2 * page_size);
> > +}
> > +
> > +static void test_mlockall_future_droppable(void)
> > +{
> > +	char *map;
> > +	unsigned long page_size = getpagesize();
> > +
> > +	if (mlockall(MCL_CURRENT | MCL_FUTURE))
> > +		ksft_exit_fail_msg("mlockall(MCL_CURRENT | MCL_FUTURE): %s\n", strerror(errno));
> Similar comments as for the other path regarding ksft_exit_fail_msg() etc.
>
> > +
> > +	map = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE,
> > +		   MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
> > +
> > +	if (map == MAP_FAILED) {
> > +		if (errno == EOPNOTSUPP) {
> > +			ksft_test_result_skip("%s: MAP_DROPPABLE not supported\n", __func__);
> > +			return;
> > +		}
> > +		ksft_exit_fail_msg("mmap error: %s\n", strerror(errno));
> > +	}
> > +
> > +	ksft_test_result(!unlock_lock_check(map, false), "%s: droppable memory not locked\n",
> > +			__func__);
> > +
> > +	if (munlockall()) {
> > +		munmap(map, 2 * page_size);
> > +		ksft_exit_fail_msg("munlockall() %s\n", strerror(errno));
> > +	}
> > +
> >   	munmap(map, 2 * page_size);
> >   }